Most vacuum cleaners use an impeller which rotates inside a chamber to draw working air through the vacuum unit. The working air drawn in by the impeller must be exhausted continuously during operation of the vacuum unit, and thus the design of the surrounding motor housing is of utmost importance. A properly designed motor housing can greatly enhance the efficiency of the vacuum unit, and can also serve to minimize excess noise created by the air flowing through the vacuum cleaner.
In order to exhaust the working air from within the motor housing, the peripheral sidewall of the motor housing is typically equipped with a plurality of blades or vanes separated by a plurality of exhaust openings. The flow of air through the exhaust openings can be altered by changing the number, size and shape of the exhaust openings and the sidewall vanes. With each rotation of the impeller, a portion of the working air within the housing is exhausted, while the remaining or excess portion of the air remains within the housing. In order to minimize noise, this excess air must be smoothly reintroduced into the flow pattern.
A variety of vane shapes have been employed in an effort to increase efficiency and minimize noise. U.S. Pat. No. 4,669,952 discloses a quiet by-pass vacuum motor having a fan end bracket with separating wedges or members which extend from an outer wall to an inner wall and which define passageways to exhaust vents, while U.S. Pat. No. 4,859,144 discloses a two-stage motor fan system. Other approaches to minimizing noise include employing irregularly shaped impeller blades, as disclosed in U.S. Pat. No. 3,398,866.
Nevertheless, there exists a continuing need for an improved motor housing design that will result in improved efficiency and that will minimize noise. There also exists a need for an improved housing design that is cost effective to produce using standard molding practices.